Method of forming shielded conductors



May 22, 1951 R. E. WALSH usmon 0F FORMING SHIELDED CONDUCTORS Filed Feb. 21, 1946 D/EL E C Z'E/C MA TEE/AL.

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Patented May 22, 1951 METHOD OF FORMING SHIELDED CONDUCTORS Ralph E. Walsh, Long Branch, N. J., assignor to Breeze Corporations, Inc., Newark, N. J a corporation of New Jersey Application February 21, 1946, Serial No. 649,300

4 Claims. I

This invention relates to the method of making shielded cables such as are commonly used in airplane and similar structures to prevent electrical interference with the reception or transmission of radio signals.

An object of this invention is to provide for the inexpensive construction of relatively light weight shielded cables.

.Another object of this invention is to provide a method of forming shielded cables of any required cross-section, area and length.

Another object of the invention is to cover an insulated wire with metallic particles and thereafter apply a coating of dielectric thereto by extrusion.

A further object of this invention is to provide a method of forming shielded cables having the desired properties requisite for the conditions under which they are to operate.

A feature of this invention is the simplicity of its construction and the uniformity of result.

These objects are accomplished by the novel construction, combination and. arrangement of parts, as herein illustrated, described and claimed.

In the accompanying drawings, forming part hereof, is illustrated one embodiment of the invention, in which drawings similar reference characters designate corresponding parts, and in which:

Figure 1 is a fractional schematic sectional view of the apparatus in use.

Figure 2 is a transverse sectional view taken on line 2--2 of Figure 1.

Figure 3 is a transverse sectional view of the shielded cable, taken on line 33 of Figure 1.

Referring to Figure 1 of the drawings, the apparatus will be seen to comprise a funnel-shaped hopper l having a large internally threaded upper opening H and a small orifice H2 at the bottom thereof. Said hopper III is of a sufficiently thick walled construction to withstand the internal pressures set up during the operation of the device.

A partitioning hopper I3, smaller than but of substantially the same shape as the outer hopper I0, is positioned within said outer hopper l0 and divides the space therein into two chambers M, I5.

A threaded flange l6 integral with the larger opening of the partitioning hopper I3 engages the internal threads ll of the outer hopper in to form an airtight union. Internal threads I! cut in the larger opening of the partitioning hopper I3 receive a cover plate l8. The cover 2 plate I!) provides an airtight seal for the upper opening of the partitioning hopper l3.

Three internally threaded holes bored in the cover plate l8 giveingress to the inner chamber M. The central hole l9 supports and positions a guide tube 28 through which the insulated wire 2! is fed. Said guide tube 20 extends from the cover plate [8 into the inner chamber id, but ends short of the sloping inner walls of the partitioning hopper l3.

A port is provided in the cover plate l8 through which the supply of metallic particles 23 may be replenished. A threaded plug 22 seals this port while the apparatus is in use. Said plug 22 pre- 3 vents the escape of compressed air which enters the inner chamber [4 through a port in the cover plate It by way of a tube 24. This air pressure is used to urge the metal into the insulation of the wire 2|.

The outer chamber i5 constitutes a reservoir from which a plastic cable covering is extruded.- A port is provided in the wall of the outer chamber l5 through which the said chamber l5 may be refilled with plastic 25, as needed. A threaded plug 26 seals this port, while the plastic is being extruded through the small orifice 12 by means of compressed air. The compressed air enters the outer chamber [5 by way of a tube 21 which is threaded into a port in the chamber wall.

The operation of this invention becomes apparent from an examination of the attached drawings. When the continuously fed insulated wire 2| leaves the end of the guide tube is the compressed air entering the chamber I through the port 24 forces the metal particles 23 into the wires dielectric covering. Said covering is of suificient permeability to receive the metallic particles 23 into the surface thereof. As the insulated wire 2| passes through the small aperture at the bottom of the partitioning hopper [3 more pressure is applied to the metal particles 23. The small aperture acts as a die to constrictably force the particles 23 into the dielectric covering of the wire 2| and into intimate contact with one another, and also to regulate the amount of flow.

A plastic covering 25 is next applied over the metalized insulated wire 2 I. This is accomplished as the wire 2| passes through the outer chamber [5 and leaves the hopper l0. Compressed air entering through the opening 26 in the hopper l0 urges the plastic 25 therein around the metalized insulated wire 21. The constricting orifice l2 at the bottom of the hopper I0 regulates the shape and thickness of the extruded plastic covering 25.

The finished cable, as shownin Figure 3, is

composed of the insulated wire 2| around which is located the metallic particles 23 and the whole encased in a plastic sheath 25.

The amount of compressed air entering the inner chambe 14 and the outer chamber 15 is carefully controlled by valves (not shown) to prevent the pressure on the plastic 25 in the hop per I9 from being forced upward into the inner chamber M. It is desirable, moreover, that said. pressures remain constant once the proper adjustments have been made.

The invention as described is extremely adaptable in its use, inasmuch as the nature of the metallic particles 23 may be changed when desired. It is possible, therefore, when using this device, to place a mixture of metal particles, having distinct electrical characteristics to satisfy particular requirements, in the inner chamber l4. Thus the particles 23 may be non-magnetic but of high electrical conductivity as, for example, powdered copper, aluminum or silver, or any desired mixture of such metals. Where it is proposed to shield against long-range frequencies the powdered metal 23 placed in the inner chamber I4 may be' a combination of one or more nonmagnetic metals and a paramagnetic metal or highpermeability, such as iron or nickel.

It is also possible, by using this invention, to change the nature of the plastic covering 25 of the cable. Although the plastic must be soft and capable of extrusion. it maybe any synthetic plastic resin such as vinyl or polystyrene.

It is important in the fabrication of this shielded cable that the metal particles 23 form a layer of suflicient thickness to completely attenuate the electrical energy radiated by the Wire 2!. In

this manner a path of low resistance will be provided along the cable through'which said radiations will be conducted.

Another form of this invention operates without the ports covered by the threaded plugs 22, 25. In this embodiment of the invention the metallic particles 23 and the dielectric plastic 25 are introduced into their respective hoppers through the p01 L's provided for their air lines 24, 21.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent of the United States, is:

1. A method of forming a flexible radio shielded cable consisting of continuously passing an insulated wire through a funnel shaped hopper, said hopper having metal particles therein, forcing a portion of the metal particles into the insulation of the wire as it passes through the restricted part of the hopper so as to press said particles into intimate contact with one another and thereafter applying a dielectric covering around said pai'ticlesof metal.

2. A method of forming a flexible radio shielded cable consisting of continuously passing an insulated wire through a multi-chambered funnel shaped hopper, said hopper having metal particles therein, forcing a portion of the metal particles into the insulation of the wire as it passes through the restricted part of the hopper so as to press said particles into intimate contact with one another and thereafter applying a dielectric covering around said particles of metal.

3. A method of forming a flexible radio shielded cable consisting of continuously passing an insulated wire through a multi-chambered funnel shaped hopper, said hopper having metal pari ticles therein, introducing compressed air into said hopper chambers, thereby forcing a portion of the metal particles into the insulation of the wire as it passes through the restricted part of the hopper so as to press said particles into intimate contact with one another and thereafter applyin a dielectric covering around said particles of metal.

4. The method forming a flexible radio shield ed cable comprising the steps of continuously passing an insulated wire through a multi-chambered hopper, introducing a supply of metal particles into said hopper, thereafter introducing compressed air into the chamber so as to force the metal particles into the insulation of said I wire, introducing a supply of dielectric material into a second chamber and thereafte applying compressed air to said second chamber in the hopper, thereby causing the said dielectric to cover the particles of metal upon the Wire.

RALPH E. WALSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 4,389 Drummond Feb. 20, 1846 392,193 Campbell Oct. 30, 1888 876,755 Webb Jan. 14, 1908 1,347,184 Smith July 20, 1920 1,681,566 Anderegg Aug. 21, 1928 1,851,182 Hendey et a1 May 31, 1932 1,951,175 Smith Mar. 13,1934 1,987,508 Johns'et al Jan. 8, 1935 2,111,229 Thompson Mar. 15, 1938 1,298,085 LeTourneau et al. Apr. 23, 1940 2,211,424 Holslag Aug. 13, 1940 2,253,069 Eckel' et al Aug. 19, 1941 2,389,705 Wetzel Nov. 27, 1945 

